1. Technical Field of the Invention
The present invention relates to a telecommunications network and, in particular, to the provision of a paging message broadcast towards a mobile station within a Public Land Mobile Network (PLMN).
2. Description of Related Art
With the introduction of the Global System for Mobile (GSM) communication and the Personal Communications System (PCS), the concepts of wireline telephone service and wireless telephone service have changed drastically. Instead of assigning a telephone number to a particular geographic location, GSM or PCS teaches the assignment of a telephone number to a particular subscriber. As a result, each subscriber is associated with a Subscriber Identity Module (SIM) card. Using an SIM card, a mobile subscriber is able to store necessary mobile subscriber information in a detachable memory unit and thereafter freely associate the module with any available mobile station. Such information includes a mobile subscriber's Mobile Station Integrated Service Digital Network (MSISDN) number, and other user specified information, such as preferred speed dialing lists or screening lists. By inserting a mobile subscriber's SIM card into a mobile station, the stored subscriber information in the inserted SIM card is available to the mobile subscriber's new terminal. As a result, the mobile subscriber is able to freely utilize any available mobile station while maintaining the same MSISDN number and subscriber feature data.
Furthermore, in order to enable the mobile subscriber to utilize the associated mobile station as a cordless phone for charging purposes while traveling within a certain geographic location, the concept of a "home zone" has been introduced. If the mobile subscriber makes a call within his or her home zone, the mobile station functions as a conventional cordless phone and the mobile subscriber is not charged for the air time, or is charged at a significantly lower air time rate. Accordingly, within his or her home zone, the mobile subscriber can utilize his or her mobile station to originate outgoing calls without incurring expensive air time charges and without physically using a different telephone terminal, e.g., wireline terminal such as a cordless phone.
With a conventional cordless terminal, a radio frequency range between the serving base unit and the cordless terminal is rather limited. Consequently, a subscriber is not able to travel out of the immediate vicinity of the base unit and make outgoing calls. However, with a PCS or GSM based telecommunications network, even if the mobile subscriber is within the home zone, the telecommunications service is still being provided by the same mobile switching center (MSC) serving that particular geographic location. Therefore, within the conventional cordless system, it was the physical limitation that imposed the geographic boundaries of the service area. In contrast, within the GSM or PCS network, it is the logical limitation that imposes the geographic boundaries of the mobile subscriber's home zone. Accordingly, the home zone associated with a particular mobile subscriber can be much larger than what was previously available with the conventional cordless system. Such a home zone may include only a few locks from the subscriber's home or business, or a radius of half mile, for example, covering a certain location.
Home zones are designated because, statistically, mobile subscribers tend to spend a great amount of time in one fixed location. Accordingly, a favorable billing rate is provided as long as a particular mobile subscriber is located within his or her designated home one. Normally, such home zones designated by mobile subscribers are much smaller than the location areas (LA) associated with those home zones. As an illustration, a typical location area may include hundreds or even thousands of cell areas (CA), whereas a home zone might typically cover only a few cell areas within a location area.
Whenever an incoming call is received towards the mobile station located within the designated home zone, the serving MSC needs to page the called mobile station. Because the serving MSC has no means of determining which cell area is currently serving the called party mobile station until the mobile station responds to the page, the serving MSC must broadcast paging messages throughout the whole location area. Utilization of paging channels (PCH) associated with hundreds or even thousands of involved cell areas (CA) to page a single mobile station locate within a much smaller home zone is a rather inefficient and wasteful use of system resources.
Accordingly, there is a need for a mechanism to page a mobile station more efficiently and effectively when the mobile station is currently traveling within its designated home zone.